How tall and short trees can coexist in old growth forests

Forests are shaped by light competition. The trees that grow the tallest have access to the most sunlight, blocking the rays and rendering the shaded space around them inhospitable to shorter trees below. In this stem exclusion phase of forest succession, the shorter trees often die. Yet scientists have observed that in old-growth forests, trees of vastly different sizes successfully coexist, proving that reaching the top of the canopy is not the sole winning strategy for survival in a forest environment.